Ultrafast Proton and Electron Transfer Dynamics in Confined and Heterogeneous Systems

Abstract

Modern scientific and technological advances have been driven by the increasing ability to control physical and chemical reactions. This pursuit naturally shifted toward observing and governing ever smaller and faster processes. From the earliest observations of chemical reactions to the first microscopic views of cells and tissues, humans have consistently tried to understand structures and processes that lie beyond what we can directly see. The invention of the microscope opened a spatial window into the microscopic world, enabling researchers to visualize biological structures and, eventually, molecular assemblies. As experimental capabilities approached the scales of molecules, atoms, and even subatomic particles, long-standing questions surrounding proton and electron motion, recognized as central to the chemistry of life and materials, became accessible. Ideas such as the Grotthuss mechanism of proton conduction in water (Grotthuss, 1806) and the theoretical frameworks describing electron transfer (Marcus, 1956) gained significance once their ultrafast dynamics could be experimentally interrogated. Understanding how these elementary particles transfer and interact with their environment is essential for deciphering reaction pathways, energetics, and the governing principles of chemical reactivity. Time-resolved spectroscopies provided the methodological breakthrough that enabled such investigations. Following the emergence of femtosecond laser technology led to the birth of femto-chemistry (Zewail, 1990), allowing direct observation of proton and electron dynamics on their intrinsic timescales. Techniques such as transient absorption and time-resolved fluorescence opened a temporal window into reaction coordinates, revealing how ultrafast motion of fundamental particles shapes chemical reaction dynamics. These advances not only improved our understanding of fundamental reactions but also provided the basis for developing functional materials. In this thesis, I present studies on proton transfer reactions of photoacid probe, as well as charge-carrier dynamics occurring within organic energetic materials. These comprehensive investigations aim to provide insight into how fundamental processes, such as proton transfer and the transfer of electrons and holes, govern and modulate a wide range of phenomena across diverse chemical and material systems.